Cleaning solution production systems and methods, and plasma reaction tanks

ABSTRACT

A cleaning solution production system is for cleaning a semiconductor substrate. The system includes a pressure tank, a plasma reaction tank configured to form a plasma in gas bubbles suspended in a decompressed liquid obtained from the pressure tank to thereby generate radical species in the decompressed liquid, a storage tank configured to store a cleaning solution containing the radical species generated in the plasma reaction tank, and a nozzle configured to supply the cleaning solution from the storage tank to a semiconductor substrate.

A claim of priority is made to Korean Patent Application No.10-2018-0088438 filed Jul. 30, 2018, in the Korean Intellectual PropertyOffice, the disclosure of which is incorporated herein by reference inits entirety.

BACKGROUND

The present disclosure relates to the production of cleaning solutions,particularly the production of cleaning solutions that may be utilizedin the fabrication of semiconductor devices.

In the fabrication of semiconductor devices, cleaning processes arecarried out to remove residues produced, for example, during etchingprocesses and the like. Typically, these cleaning processes includeexposing a wafer containing the semiconductor devices to a cleaningsolution such as cleaning water. Unfortunately, the cleaning solutionmay unintentionally damage semiconductor patterns of the semiconductordevices, such a metal films formed in active areas of the semiconductordevices. This is because the cleaning solution typically includessulfuric acid or hydrofluoric acid which can result in corrosion andoxidation of exposed metals of the semiconductor devices. Separately,the acids contained in the cleaning solutions make disposal of usedcleaning solutions environmentally costly.

SUMMARY

According to an aspect of the present disclosure, a cleaning solutionproduction system for cleaning a semiconductor substrate is provided.The system includes a pressure tank, a plasma reaction tank configuredto form a plasma in gas bubbles suspended in a decompressed liquidobtained from the pressure tank to thereby generate radical species inthe decompressed liquid, a storage tank configured to store a cleaningsolution containing the radical species generated in the plasma reactiontank, and a nozzle configured to supply the cleaning solution from thestorage tank to a semiconductor substrate.

According to another aspect of the present disclosure, a plasma reactiontank is provided. The plasma reaction tank includes a vessel configuredto contain a decompressed liquid including gas bubbles suspended in thedecompressed liquid, first and second electrodes located at oppositesides of the vessel, the first and second electrodes shielded toprevented any contact with the decompressed liquid, at least oneignition electrode located radially between the first and secondelectrodes, the at least one ignition electrode shielded to prevent anycontact with the decompressed liquid, and a power source configured todrive the first and second electrodes and the at least one ignitionelectrode to form a plasma in gas bubbles suspended in the decompressedliquid.

According to yet another aspect of the present disclosure, a method ofcleaning a semiconductor substrate is provided. The method includesforming plasma in gas bubbles suspended in a liquid, and obtaining acleaning solution from the liquid having the plasma formed in the gasbubbles, where the cleaning solution includes a concentration of radicalspecies resulting from the plasma in the gas bubbles. The method furtherincludes supplying the cleaning solution to a semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features of the present disclosure willbecome readily apparent from the detailed description that follows, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic view of a cleaning solution production systemaccording to some exemplary embodiments of the present disclosure;

FIG. 2 is a schematic view illustrating examples of a pressurizingportion and a bubble forming portion of the apparatus of FIG. 1;

FIG. 3 is a schematic top-view of the bubble forming portion of FIG. 2;

FIG. 4 is a schematic view illustrating an example of an electrodeconfiguration of a plasma reaction tank of FIG. 1;

FIG. 5 is a schematic view for reference in describing a firstelectrode, a second electrode, and an ignition electrode of FIG. 4;

FIG. 6 is a perspective view illustrating an example of the shape of theignition electrode of FIG. 5;

FIG. 7 is a schematic view of an example of a plasma monitoring deviceof FIG. 1;

FIG. 8 is a schematic view of a cleaning solution production systemaccording to some exemplary embodiments of the present disclosure;

FIG. 9 is a conceptual perspective view illustrating an example of anelectrode configuration of a plasma reaction tank of FIG. 8;

FIG. 10 is a conceptual perspective view illustrating another example ofan electrode configuration of a plasma reaction tank of FIG. 8;

FIG. 11 is a schematic view of another example of a plasma monitoringdevice;

FIG. 12 is a flowchart for reference in describing a cleaning solutiontreatment method according to some exemplary embodiments of the presentdisclosure; and

FIG. 13 is a detailed flowchart for reference in describing a cleaningsolution forming operation of FIG. 12.

DETAILED DESCRIPTION OF EMBODIMENTS

Hereinafter, systems and methods for producing a cleaning solutionaccording to some exemplary embodiments of the present disclosure willbe described with reference to the drawings.

FIG. 1 is a schematic view of a cleaning solution production systemaccording to some exemplary embodiments of the present disclosure, FIG.2 is a schematic view of an example of a pressurizing portion and abubble forming portion of the system of FIG. 1, and FIG. 3 is a top viewof a bubble formation device of the bubble forming portion of the systemof FIG. 1.

Referring to FIG. 1, the cleaning solution production system accordingto some exemplary embodiments of the present disclosure includes apressurizing portion 100, a bubble forming portion 200, a plasmareaction tank 300, a first pipe 400, a storage tank 500, a radicalsensor 600, a second pipe 700, and a nozzle 800.

For purposes of illustration, in the drawings a first direction X and asecond direction Y are horizontal directions which intersect with eachother. For example, the first direction X and the second direction Y maybe perpendicular to each other. A third direction Z is a verticaldirection which intersects with the first direction X and the seconddirection Y. For example, the third direction Z may be perpendicular toboth the first direction X and the second direction Y. Accordingly, anyof the first direction X, the second direction Y, and the thirddirection Z may be orthogonal to any other of the first direction X, thesecond direction Y, and the third direction Z.

The pressurizing portion 100 in the example of FIG. 1 includes apressure tank 105, a gas inlet 110, a liquid forced-transfer portion120, and a liquid inlet 130. The liquid forced-transfer portion 120 maybe a path through which a liquid enters the pressurizing portion 100. Inparticular, in the example of FIG. 1, the liquid forced-transfer portion120 is a path through which a cleaning solution S generated in theplasma reaction tank 300 and circulated through the first pipe 400, thestorage tank 500, the radical sensor 600, and the second pipe 700 isinjected into the pressure tank 105.

Also, the liquid forced-transfer portion 120 may additionally inject aliquid solvent received through the liquid inlet 130 into the pressuretank 105. In the example of FIG. 1, the liquid inlet 130 is located at aside surface of the second pipe 700 connected to the liquidforced-transfer portion 120. However, the location of the liquid inlet130 is not limited. The liquid solvent may, for example, be at least oneof distilled water, carbonated water, electrolyte-ionized water, andcleaning water. However, the embodiments are not limited to theseexamples.

The gas inlet 110 of the example of this embodiment is a path throughwhich a gas is injected into the pressure tank of the pressurizingportion 100. The gas is for generating radicals in the cleaning solutionS, and the type of gas is dependent upon the type of radicals to beused. Examples of the gas injected through the gas inlet 110 include O₂,H₂, N₂, NF₃, CxFy, F₂, Cl₂, Br₂, He, Ar, and mixtures of two or morethereof. However, the type of the gas is not limited thereto.

A gas for generating radicals in the cleaning solution S may be insertedthrough the gas inlet 110. Depending on the type of radicals that areused, the type of the gas injected into the gas inlet 110 may differ.The type of the gas which is injected may include, for example, at leastone of O₂, H₂, N₂, NF₃, CxFy, F₂, Cl₂, Br₂, He, Ar, and a mixturethereof (where x and y are positive integers). However, the embodimentsare not limited to these examples.

In one example, when oxygen O₂ is injected via the gas inlet 110, theoxygen is coupled to a liquid such that radicals of at least one of OH,O, O₂, O₃, HO₂, H₃O, and H may be contained in the cleaning solution S.On the other hand, when other gases are used, radicals of at least oneof NO, NO₂, NO₃, CO₂, CO₃, Cl, F, Br, BrO, Cl, ClO, and HF₂ may becontained in the cleaning solution S.

Generally, a radical is formed when a reaction occurs due to stimulisuch as light, heat, or electricity, and refers to an atom that has anunpaired odd electron or a substance having high reactivity when beingformed as a compound. As such, radicals do not remain stable and mayexist for a relatively short lifetime and then disappear. Due to thesubstantially high reactivity thereof, radicals may result indecomposition reactions of organic and inorganic materials which are tobe objects of cleaning.

The cleaning solution S of the cleaning solution production systemaccording to some exemplary embodiments of the present disclosure mayperform cleaning by decomposing a polymer compound using such radicals.This may prevent a metal pattern from being eroded and oxidized, incomparison to an existing cleaning method using sulfuric acid or fluoricacid. Also, since radicals revert to a harmless liquid or gas such aswater, oxygen, or the like upon the lapse of a relatively shortlifetime, there is minimal environmental impact.

The gas inlet 110 is connected to the liquid forced-transfer portion 120in which the liquid inlet 130 is formed such that a solvent and a gasmay be mixed with each other. For example, the gas inlet 110 may beconnected to a middle portion of the liquid forced-transfer portion 120such that a gas and a solvent may be mixed with each other according toa flow of the solvent.

The pressurizing portion 100 includes the pressure tank 105 toaccommodate a mixture M in which a gas and a liquid are mixed. Themixture M may be formed by mixing the gas and the liquid according toinjection rates thereof.

A pressurizing pump (not shown) may be present in the pressurizingportion 100. The pressurizing pump operates to increase pressure in thepressurizing tank 105. When the pressure is increased by thepressurizing pump, a concentration of the gas in the mixture M mayincrease beyond saturation. In this way, the mixture M may become acompressed liquid of, for example, supersaturated gas-dissolved water inwhich the gas to be supersaturated is dissolved.

When the mixture M becomes the cleaning solution S and is circulated inthe plasma reaction tank 300 and returns to the pressurizing portion100, the cleaning solution S, rather than the mixture M, may beaccommodated in the pressure tank 105 of the pressurizing portion 100.

The bubble forming portion 200 may be operatively connected to thepressurizing portion 100 in order to create bubbles in the compressedliquid received from the pressure tank 105. Referring to FIG. 3, in theexample of this embodiment, the bubble forming portion 200 isconstituted by a partition plate 210 having orifices 220 formed therethrough. Referring to FIG. 2, the partition plate 210 is operativelyinterposed between the pressure tank 105 and the plasma reaction tank300, with the orifices 220 providing fluid communication from thepressure tank 105 to the plasma reaction tank 300. It is noted that therelative width of the orifices 220 is not necessarily drawn to scale inthe drawings. Generally, the width of the orifices 220 is very small soas to form bubbles in the liquid introduced into the plasma reactiontank 300 from the pressure tank 105.

Optionally, the orifices 220 may be closed until the mixture M issupersaturated, and then may be opened. A resultant pressuredifferential causes the compressed mixture M to rapidly move from thepressure tank 100 to the plasma reaction tank 300 through the orifices220 of the partition plate 210, and accordingly, bubbles B are formed ina decompressed liquid mixture M contained in the plasma reaction tank300. Here, the phrase “decompressed liquid” means the liquid mixture Mthat was compressed in the pressure tank and then decompressed uponintroduction into the plasma reaction tank 300. The bubbles B may bebubbles of the gas injected through the gas inlet 110. That is, the gasinjected through the gas inlet 110 may be present in the bubbles B.

Although an outer periphery of the partition plate 210 of the bubbleforming portion 200 is shown as being of a circular shape in FIG. 3, theembodiments are not limited thereto. That is, the outer circumferentialsurface of the partition plate 210 of the bubble forming portion 200 mayhave a quadrangular shape, an oval shape, or any other suitable shape.

Referring again to FIG. 1, the plasma reaction tank 300 includes firstand second electrodes 310 and 320 respectively shielded by first andsecond covers 311 and 321, as well as an ignition electrode 330. Theseelectrodes constitute an electrode configuration which will be describedin greater detail below with reference to FIGS. 4-6.

FIG. 4 is a schematic view illustrating an example of an electrodeconfiguration of the plasma reaction tank of FIG. 1, and FIG. 5 is aschematic view for reference in describing a first electrode, a secondelectrode, and an ignition electrode of FIG. 4. FIG. 6 is a perspectiveview illustrating an example of the shape of the ignition electrode ofFIG. 5.

Referring to FIGS. 1 and 4 to 6, the plasma reaction tank 300 receivesliquid (mixture M) from the pressure tank 105 through the bubble formingportion 200. As explained above, the liquid in the pressure tank 105 isdecompressed relative to that in the pressure tank 105, and includesbubbles that are formed as the liquid is passed through the bubbleforming portion 200. As a result, gas bubbles are suspended in thedecompressed liquid of the pressure tank 105.

In the present embodiment, the mixture M in the plasma reaction tank 300is converted to a cleaning solution S by formation of plasma within thegas bubbles suspended in the mixture M. The formation of plasma isaccomplished by application of voltages to the electrodes 310, 320 and330.

As shown in the drawings, the first electrode 310 may be formed on oneside surface of the plasma reaction tank 300. The first electrode 310may be embedded in an outer wall of the plasma reaction tank 300.Otherwise, the first electrode 310 may be covered by a first coating 311in the plasma reaction tank 300. The first coating 311 may act as ashield to block and prevent the cleaning solution S or the mixture Mfrom coming into direct contact with the first electrode 310.

The first electrode 310 may include an electrical conductor. Forexample, the first electrode 310 may be formed of a metal. On the otherhand, the first coating 311 may include an insulator. For example, thefirst coating 311 may be formed of a non-metallic ceramic material.

The second electrode 320 may be formed on a side surface of the plasmareaction tank 300 opposite that of the first electrode 310. In theexample of the drawings, the second electrode 320 is located on theother side spaced apart from the first electrode 310 in the firstdirection X in the plasma reaction tank 300. With this configuration,the first electrode 310 and the second electrode 320 may apply anelectric field to the mixture M located between the first electrode 310and the second electrode 320.

The second electrode 320 may also be embedded in an outer wall of theplasma reaction tank 300. Otherwise, the second electrode 320 may becovered by a second coating 321 in the plasma reaction tank 300. Thesecond coating 321 may act as a shield to block and prevent the cleaningsolution S or the mixture M from coming into direct contact with thesecond electrode 320.

The second electrode 320 may include an electrical conductor. Forexample, the second electrode 320 may be formed of a metal. On the otherhand, the second coating 321 may include an insulator. For example, thesecond coating 321 may be formed of a non-metallic ceramic material.

As shown in FIG. 4, the first electrode 310 may be electricallyconnected to a ground terminal 340 by a wiring 370. The second electrode320 may be electrically connected to a power source 350 by the wiring370. The power source 350 may be electrically connected between thesecond electrode 320 and the ground terminal 340.

A switch 360 may be located on the wiring 370 between the secondelectrode 320 and the power source 350. A switching operation of theswitch 360 may control a connection between the second electrode 320 andthe power source 350. That is, when the switch 360 is closed, the secondelectrode 320 is connected to the power source 350. When the switch 360is opened, the second electrode 320 is not connected to the power source350.

The power source 350 may be a direct current (DC) power source or may bean alternating current (AC) power source. The power source 350 may be,for example, a radio frequency (RF) pulse power source, but theembodiments are not limited in this fashion.

The ignition electrode 330 may be located radially between the firstelectrode 310 and the second electrode 320. That is, as shown in thedrawings, the ignition electrode 330 may be disposed relative to thefirst direction X between the first electrode 310 and the secondelectrode 320 in the first direction X.

In the example of the present embodiments, the ignition electrode 330 isdisposed below or at a bottom region the plasma reaction tank 300. Alsoin the example of the present embodiments, the ignition electrode 330does not overlap an area defined between the first electrode 310 and thesecond electrode 320. That is, the ignition electrode 330 is locatedrelative to the Z direction below the region defined between the firstelectrode 320 and the second electrode 320.

The ignition electrode 330 may be connected to the power source 350 bythe wiring 370. The ignition electrode 330 may be covered by a thirdcoating 331. The third coating 331 may act as a shield to block andprevent the cleaning solution S or the mixture M from coming into directcontact with the ignition electrode 330.

The ignition electrode 330 may include a conductive material. Forexample, the ignition electrode 330 may be formed of a metal. On theother hand, the third coating 331 may include an insulator. For example,the third coating 331 may be formed of a non-metallic ceramic material.

As described next, plasma is formed in the plasma reaction tank instages by powering the first, second and ignition electrodes 310, 320and 330.

In a first plasma formation stage, the switch 360 is open such that thepower source 350 is initially applied to the ignition electrode 330.Through this, the ignition electrode 330 may ignite plasma so as to formignition plasma in a first region R1.

Subsequently, in a second plasma formation stage, the switch 360 isclosed so as to apply the power source 350 to the second electrode 320.Through this, active plasma may be formed in a second region R2 by usingthe applied power to the first and second electrodes 310 and 320.

Igniting the plasma in the first region R1 in the first plasma formationstage facilitates formation of the active plasma by the first and secondelectrodes 310 and 320 in the second plasma formation phase. Inparticular, a much higher ignition energy would be needed to ignite theactive plasma in the second region R2 using the first and secondelectrodes 310 and 320 only, i.e., without first igniting plasma in thefirst region R1 using the ignition electrode 330. The higher ignitionenergy that would be needed runs the danger of damaging the plasmareaction tank 300. Application of lower energy is made possible byinitially igniting plasma using the ignition electrode 330 as describedabove.

Referring to FIG. 6, the ignition electrode 330 may include a first baseportion 332, a second base portion 333, and a protruding portion 334.The first base portion 332 may have a first height h1. The first baseportion 332 may extend to the same height in a second direction Y.

The second base portion 333 may have the first height H1 like the firstbase portion 332. The second base portion 333 may extend to the sameheight in the second direction Y.

The protruding portion 334 may be located between the first base portion332 and the second base portion 333 in the first direction X. Theprotruding portion 334 may have a second height h2. The second height h2may be higher than the first height h1. The protruding portion 334 mayextend to the same height in the second direction Y.

Accordingly, the ignition electrode 330 may be a bar electrode which hasan upside-down T-shaped cross section and extends lengthwise in thesecond direction Y. However, the embodiments are not limited in thisfashion.

The plasma reaction tank 300 may apply a voltage to the mixture M usingthe above-described method. Accordingly, a gas in the bubbles B of themixture M may be converted into plasma. Such plasma may be defined asbubble liquid plasma. The plasma reaction tank 300 may convert themixture M into the cleaning solution S including the bubble liquidplasma.

The cleaning solution S may include radicals which are dissolved in thebubble liquid plasma. The radicals may be dissolved in the cleaningsolution S in the bubble liquid plasma while the cleaning solution Scirculates through the plasma reaction tank 300, the first pipe 400, thestorage tank 500, the radical sensor 600, the second pipe 700, thepressurizing portion 100, and the bubble forming portion 200.

Although the radicals may dissipate during circulation due to a shortlifetime thereof, the plasma reaction tank 300 may regenerate radicalsby applying a voltage. Accordingly, the cleaning solution S maycontinuously include radicals regardless of dissipation of radicalsduring circulation.

Referring back to FIG. 1, a plasma monitoring device 900 may be providedin order to check for a type and a concentration of radicals of thecleaning solution S in the plasma reaction tank 300. The plasmamonitoring device 900 may also check a type of gas of the bubbles B inthe cleaning solution S.

The plasma monitoring device 900 according to some exemplary embodimentsof the present disclosure may monitor whether a plasma reaction forgenerating radicals is performing properly by checking the type and theconcentration of each of the gas and the radicals in the plasma reactiontank 300.

When an intended type of radicals is not generated or an intendedconcentration of radicals is not formed, a plasma reaction may beadjusted by adjusting a flow rate or type of an injected gas.

The plasma monitoring device 900 according to some exemplary embodimentsof the present disclosure measures a type and a concentration ofradicals by using an electrical measuring method. The electricalmeasuring method monitors the type and concentration of radicals byanalyzing electrical properties of liquid plasma including a dielectric.That is, the electrical measuring method may electrically analyzedensities and properties of the bubbles B and plasma. For this, theplasma monitoring device 900 may include a power source and an electrode(not shown). Through this, a voltage or a current may be applied to thecleaning solution S and electrical characteristics such as resistancemay be detected so as to measure the type and the concentration of theradicals.

In another example, the plasma monitoring device 900 according to someexemplary embodiments of the present disclosure measures a type and aconcentration of radicals by using a microwave analysis method. Themicrowave analysis method may analyze a density of in-liquid plasma byutilizing wave dispersion relation of microwaves.

In another yet example, the plasma monitoring device 900 according tosome exemplary embodiments of the present disclosure may measure a typeand a concentration of radicals by using an optical analysis method asdescribed next.

FIG. 7 is a schematic view for describing an example of the plasmamonitoring device of FIG. 1.

Referring to FIGS. 1 and 7, the plasma monitoring device 900 may belocated outside the plasma reaction tank 300.

The plasma reaction tank 300 may include a tank body 301 and a window302. The tank body 301 is a housing of the plasma reaction tank 300 andmay refer to an outer wall part which accommodates the cleaning solutionS.

The window 302 may be formed in the tank body 301. The window 302 may beformed of a transparent material to allow an inside of the plasmareaction tank 300 to be monitored from the outside. Due to plasmatherein, the bubbles B in the plasma reaction tank 300 may autonomouslyemit light. Light L generated by the bubbles B may be sensed by theplasma monitoring device 900 through the window 302.

The plasma monitoring device 900 may sense the light L and analyze atype of a plasma gas, a temperature of a gas, and a relative density ofplasma so as to measure a type and a concentration of radicals of thecleaning solution S.

In the example of this embodiment, the plasma monitoring device 900 is ameasuring module using optical emission spectroscopy (OES).

Since the plasma monitoring device 900 monitors a radical generationreaction of the plasma reaction tank 300, it is possible to check inreal time whether generation of the cleaning solution S is beingproperly performed.

Referring back to FIG. 1, the first pipe 400 may be connected to theplasma reaction tank 300. The first pipe 400 may connect the plasmareaction tank 300 to the storage tank 500. The first pipe 400 maytransfer the cleaning solution S in the plasma reaction tank 300 to thestorage tank 500.

Although the first pipe 400 is shown as being connected in the thirddirection Z of the plasma reaction tank 300 in FIG. 1, this is merely anexample and the embodiment is not limited thereto.

The storage tank 500 may be connected to the first pipe 400. The storagetank 500 may be a space in which the cleaning solution S containing theradical species generated in the plasma reaction tank 300 is stored. Thestorage tank 500 may be connected to the first pipe 400, the radicalsensor 600, and a nozzle 800.

The storage tank 500 may include a first valve 810 and a second valve820. The first valve 810 may be located in a part connecting the storagetank 500 to the nozzle 800. The first valve 810 may be closed and thenopened responsive to the radical sensor 600 so as to move the cleaningsolution S to the nozzle 800.

The second valve 820 may be located in a part connecting the storagetank 500 to the radical sensor 600. The second valve 820 may be openedand then be closed by the radical sensor 600 so as to prevent thecleaning solution S from passing there through.

The operations of the first valve 810 and the second valve 820 will bedescribed below in more detail.

The radical sensor 600 may sense a concentration of radicals of thecleaning solution S of the storage tank 500 using any of a variety ofmethods.

For example, the radical sensor 600 may sense the concentration ofradicals of the cleaning solution S by using a spectroscopic method. Thespectroscopic method may be a method of measuring a generation speed anda dissipation speed of a radical reaction product, a consumption factor,or a probe compound by using non-dispersive infrared (NDIR) or infrared(IR) spectroscopy. Through this, the radical sensor 600 mayquantitatively analyze radicals of the cleaning solution S.

As another example, the radical sensor 600 of the cleaning solutionproduction system according to some exemplary embodiments of the presentdisclosure may measure the concentration of radicals by using electronparamagnetic resonance (EPR). EPR may measure a type and a concentrationof radicals by using a magnetic moment measuring method using holes ofradicals or spins of electrons. Through this, the radical sensor 600 mayquantitatively and qualitatively analyze radicals of the cleaningsolution S.

The radical sensor 600 may direct the cleaning solution S to the nozzlewhen a concentration of particular radicals in the cleaning solution Sreaches a reference concentration. For this, the radical sensor 600 mayuse the first valve 810 and the second valve 820.

In detail, when it is determined that the concentration of particularradicals in the cleaning solution S reaches the reference concentration,the radical sensor 600 may open the first valve 810 and close the secondvalve 820. Through this, the cleaning solution S located in the storagetank 500 may directed to the nozzle 800. As such, the cleaning solutionS which circulates from the storage tank 500 to the radical sensor 600may not further circulate.

Operations as described above of the first valve 810 and the secondvalve 820 of the cleaning solution production system according to someexemplary embodiments of the present disclosure are merely an example.The cleaning solution S may be supplied to the nozzle 800 using anymethod. For example, the second valve 820 may be omitted and the radicalsensor 600 may control only the first valve 810 to supply the cleaningsolution S to the nozzle 800.

Although the radical sensor 600 is shown as being located in an outletend of the storage tank 500, the embodiments are not limited thereto.The radical sensor 600 may instead be located at an inlet end of thestorage tank 500, or elsewhere other than the outlet or inlet ends ofthe storage tank 500. Also, a position of the second valve 820 is notparticularly limited.

The second pipe 700 may extend from the radical sensor 600. The secondpipe 700 may connect the pressurizing portion 100 to the radical sensor600. The second pipe 700 may be connected to the liquid forced-transferportion 120 of the pressurizing portion 100. Through this, the cleaningsolution S may circulate in an order of the pressurizing portion 100,the bubble forming portion 200, the plasma reaction tank 300, the firstpipe 400, the storage tank 500, the radical sensor 600, and the secondpipe 700. The circulation may be continued until being stopped by theradical sensor 600.

Although the second pipe 700 is shown as extending from a bottom of theradical sensor 600, that is, a part thereof in the third direction Z,this is merely an example and the second pipe 700 is not limitedthereto.

The second pipe 700 may include a circulation pump 710 and the liquidinlet 130.

The circulation pump 710 may allow the cleaning solution S to circulatein the order of the pressurizing portion 100, the bubble forming portion200, the plasma reaction tank 300, the first pipe 400, the storage tank500, the radical sensor 600, and the second pipe 700.

A movement direction and velocity of the cleaning solution S may bedefined by the circulation pump 710. Although the circulation pump 710is shown as being located in the second pipe 700 in FIG. 1, theembodiment is not limited thereteo.

The circulation pump 710 may be attached to any position in which thecleaning solution S is present, for example, the first pipe 400 or thestorage tank 500.

The liquid inlet 130 may be formed on the side surface of the secondpipe 700. A liquid solvent of the cleaning solution S may be insertedthrough the liquid inlet 130. The liquid inlet 130 is not opened alwayssuch that the liquid is injected thereinto. When the cleaning solution Sis completely generated, the liquid inlet 130 may be closed to circulatethe cleaning solution S.

Although the liquid inlet 130 is shown as being formed in the secondpipe 700 in FIG. 1, the liquid inlet 130 may be formed in another part.For example, the liquid inlet 130 may be formed in the pressurizingportion 100.

The nozzle 800 may be connected from the storage tank 500. The nozzle800 may eject the cleaning solution S including radicals onto a wafer W.Herein, the term nozzle is broadly defined to include any device capableof controlling the direction and/or flow rate of the cleaning solution Sonto the wafer W.

The nozzle 800 may employ a central ejection method. In detail, thenozzle 800 may jet the cleaning solution S to a central part of a topsurface of the wafer W mounted on a chuck. The jetted cleaning solutionS may be developed from the central part to an edge part of the wafer Was the wafer W is rotated.

The nozzle 800 may be present in another position instead of the top ofthe wafer W in another process and may move to the central part of thewafer W to jet the cleaning solution S as needed.

The cleaning solution production system according to the embodimentsgenerates a cleaning solution by using radicals having a short lifetime.Accordingly, the cleaning solution S is continuously generated in theplasma reaction tank 300 to prevent radicals from dissipating and iscirculated such that the cleaning solution S including radicals may bestored in the storage tank 500.

The cleaning solution production system according to the embodiment mayuse the cleaning solution S using radicals without a hydrofluoric acidcomponent or a sulfuric acid component unlike existing cleaning water.Accordingly, it is possible to prevent corrosion or oxidization, whichwould otherwise be caused by the cleaning solution, of metal patterns onthe wafer W to be protected. Through this, performance and reliabilityof a semiconductor device on the wafer W may be increased.

Also, since radicals are converted into a harmless material after ashort lifetime, the cleaning solution S of the present embodiment iseco-friendly. Also, production costs of the cleaning solution S may bereduced since the use of chemical solvents may be avoided.

Hereinafter, a cleaning solution production system according to someexemplary embodiments of the present disclosure will be described withreference to FIGS. 8 and 9. A description which overlaps with theabove-described embodiments will be brief or omitted.

FIG. 8 is a schematic view of the cleaning solution production systemaccording to some exemplary embodiments of the present disclosure, andFIG. 9 is a perspective view illustrating an electrode configuration ofthe plasma reaction tank of FIG. 8. In these figures, like referencenumbers refer to like components as described above in connection withFIGS. 1-7, and accordingly, a detail description of such components isnot repeated below to avoid redundancy in the description.

Referring to FIGS. 8 and 9, the plasma reaction tank 300 of the cleaningsolution production system according to some exemplary embodiments ofthe present disclosure includes a first ignition electrode 330-1 and asecond ignition electrode 330-2.

The first ignition electrode 330-1 and the second ignition electrode330-2 may be located between the first electrode 310 and the secondelectrode 320 relative to the first direction X.

The first ignition electrode 330-1 and the second ignition electrode330-2 may be disposed below the plasma reaction tank 300 in such amanner as to not overlap an area defined between the first electrode 310and the second electrode 320. That is, the first and second ignitionelectrodes 330-1 and 330-2 may be disposed downwardly relative to thethird direction Z so as not to be interposed between confrontingsurfaces of the first and second electrodes 310 and 320.

The plasma reaction tank 300 may include a first switch 361 located onthe wiring 370 which selectively connects the power source 350 to thefirst ignition electrode 330-1. The first switch 361 may connect thepower source 350 to the first ignition electrode 330-1 when being closedand may block connection between the power source 350 and the firstignition electrode 330-1 when being opened.

The plasma reaction tank 300 may include a second switch 362 located onthe wiring 370 which selectively connects the power source 350 to thesecond ignition electrode 330-2. The second switch 362 may connect thepower source 350 to the second ignition electrode 330-2 when beingclosed and may block connection between the power source 350 and thesecond ignition electrode 330-2 when being opened.

As described next, plasma is formed in the plasma reaction tank instages by powering the first electrode, second electrode, first ignitionelectrode 330-1 and second ignition electrode 330-2.

In a first plasma formation stage, the plasma reaction tank 300 mayfirst connect the power source 350 to only the first ignition electrode330-1 by closing the first switch 361. Through this, the first ignitionelectrode 330-1 may ignite plasma so as to form ignition plasma in afirst sub-region R1-1. Here, the second switch 362 and the switch 360may be opened.

Sequentially, in a second plasma formation stage, the plasma reactiontank 300 may additionally connect the power source 350 to the secondignition electrode 330-2 by closing the second switch 362 in addition tothe already closed first switch 361. Through this, the second ignitionelectrode 330-2 may ignite plasma so as to form ignition plasma in asecond sub-region R1-2. Here, the switch 360 may be opened.

The second sub-region R1-2 may be larger than the first sub-region R1-1and may be smaller than a second region R2 formed between the firstelectrode 310 and the second electrode 320.

Sequentially, in a third plasma formation stage, the plasma reactiontank 300 may close the switch 360 so as to connect the power source 350to the second electrode 320. Through this, the first electrode 310 andthe second electrode 320 may apply voltages to the mixture M and thebubbles B therebetween. Active plasma may be formed in the second regionR2 by using the applied voltages. When the switch 360 is closed, thepreviously closed first switch 361 and the second switch 362 may remainclosed.

The plasma reaction tank 300 of the cleaning solution production systemaccording to the embodiments may subdivide a plasma ignition stage byusing a plurality of ignition electrodes. Through this, a hardwaredevice may be prevented from being damaged by minimizing energynecessary for plasma ignition.

Although the two ignition electrodes are described as an example in theembodiment, the embodiment is not limited thereto. That is, three ormore ignition electrodes may be present. In this case, ignition plasmamay be sequentially formed in each of three or more sub-regions andactive plasma may be more stably formed.

Hereinafter, a cleaning solution production system according to someexemplary embodiments of the present disclosure will be described withreference to FIG. 10.

FIG. 10 is a conceptual perspective view illustrating another example ofan electrode configuration of a plasma reaction tank of FIG. 8. In thisfigure, like reference numbers refer to like components as describedabove in connection with FIG. 9, and accordingly, a detail descriptionof such components is not repeated below to avoid redundancy in thedescription.

Referring to FIG. 10, the plasma reaction tank 300 of the cleaningsolution production system according to some exemplary embodiments ofthe present disclosure may include a first capacitor 371 and a secondcapacitor 372. The power source 350 may be an AC power source.

The first capacitor 371 may be located on a wiring where the firstignition electrode 330-1 and the power source 350 are connected. When avoltage is applied to the first ignition electrode 330-1 by the firstswitch 361, the voltage may be gradually applied due to the presence ofthe first capacitor 371. Accordingly, the possibility of damaging theplasma reaction tank 300 otherwise caused by an abrupt change in voltageapplied by the first ignition electrode 330-1 is reduced.

Similarly, when the first switch 361 is opened, the voltage may begradually removed from the first ignition electrode 330-1 due to thefirst capacitor 371. Again, this method may prevent the plasma reactiontank 300 including the first ignition electrode 330-1 from being damagedby an abrupt change in voltage.

The second capacitor 372 may be located on a wiring where the secondignition electrode 330-2 and the power source 350 are connected. When avoltage is applied to the second ignition electrode 330-2 by the secondswitch 362, the voltage may be gradually applied due to the presence ofthe second capacitor 372. Accordingly, the possibility of damaging theplasma reaction tank 300 as a result of a voltage being abruptly appliedby the second ignition electrode 330-2 is reduced.

Similarly, when the second switch 362 is opened, the voltage may begradually removed from the second ignition electrode 330-2 due to thepresence of the second capacitor 372. Again, avoidance of an abruptvoltage change applied to the plasma reaction tank 300 may reduce thelikelihood of damage.

In summary, the cleaning solution production system according to theembodiment of FIG. 10 may allow AC power to be gradually applied andremoved using the first capacitor 371 and the second capacitor 372.Accordingly, it is possible to minimize damage to the plasma reactiontank 300.

Hereinafter, a cleaning solution production system according to someexemplary embodiments of the present disclosure will be described withreference to FIG. 11. In this figure, like reference numbers refer tolike components as described above in connection with the previousfigures, and accordingly, a detail description of such components is notrepeated below to avoid redundancy in the description.

FIG. 11 is a schematic view for reference in describing anothertechnique for monitoring plasma in the plasma reaction tank 300.

Referring to FIG. 11, the plasma monitoring device 900 of the cleaningsolution production system according to some exemplary embodiments ofthe present disclosure includes an emission module 910 and a receptionmodule 920.

The plasma reaction tank 300 may include a first window 302-1 and asecond window 302-2. The first window 302-1 and the second window 302-2may be formed in the tank body 301. The first window 302-1 and thesecond window 302-2 may be formed of a transparent material to allow aninside of the plasma reaction tank 300 to be monitored from the outside.

The first window 302-1 and the second window 302-2 may be spaced apartin the second direction Y. That is, the first window 302-1 and thesecond window 302-2 may be aligned between the first and secondelectrodes 310 and 320 which are spaced apart in the first direction X(see, e.g., FIGS. 1 and 8). It is noted that the second direction Y isnot necessarily perpendicular to the first direction X.

The plasma monitoring device 900 includes the emission module 910 andthe reception module 920. The emission module 910 may emit emissionlight L1. The emission light L1 may be transmitted through the firstwindow 302-1 and may enter the plasma reaction tank 300.

While passing through the cleaning solution S and the bubbles B, theemission light L1 may become reception light L2 in which a particularwavelength is changed. The emission light L1 may be transmitted throughthe second window 302-2 and may be received by the reception module 920.

The emission module 910 and the reception module 920 may measure a typeand a concentration of radicals by using information of the emissionlight L1 and the reception light L2. Here, the plasma monitoring device900 may be a measuring apparatus using optical absorption spectroscopy(OAS).

Since the plasma monitoring device 900 may monitor a radical generationreaction of the plasma reaction tank 300, it is possible to check inreal time whether generation of the cleaning solution S is performingproperly.

Hereinafter, a cleaning water treatment method according to someexemplary embodiments of the present disclosure will be described withreference to FIGS. 1 to 7 and 12. A description which overlaps with theabove-described embodiments will be brief or omitted.

FIG. 12 is a flowchart for reference in describing a cleaning watertreatment method according to some exemplary embodiments of the presentdisclosure.

Referring to FIG. 12, a mixture is formed by mixing a liquid and a gas(S100).

In detail, referring to the example of FIGS. 1 and 2, a liquid solventof the cleaning solution S may be injected through the liquid inlet 130.For example, the solvent may be at least one of distilled water,carbonated water, electrolyte-ionized water, and cleaning water.However, the embodiments herein are not limited to these examples.

The gas inlet 110 may be a path through which a gas is injected into thepressurizing portion 100. A gas for generating radicals in the cleaningsolution S may be inserted later through the gas inlet 110. As mentionedpreviously, the type of gas injected via the gas inlet 110 is dependentupon the type of radicals to be used.

The gas inlet 110 is connected to the liquid forced-transfer portion 120in which the liquid inlet 130 is formed such that a solvent and a gasmay be mixed with each other. For example, the gas inlet 110 isconnected to a middle part of the liquid forced-transfer portion 120such that a gas and a solvent may be mixed with each other according toa flow of the solvent.

The pressure tank 105 of the pressurizing portion 100 may accommodate amixture M in which a gas and a liquid are mixed. The mixture M may beformed by mixing the gas and the liquid according to injection speedsthereof.

Referring back to FIG. 12, the gas is supersaturated (S200).

In detail, referring to the example of FIGS. 1 and 2, a pressurizingpump (not shown) may be present in the pressurizing portion 100. Thepressurizing pump operates to increase pressure in the pressurizing tank105. When the pressure is increased by the pressurizing pump, aconcentration of the gas in the mixture M may increase beyondsaturation. In this way, the mixture M may become a compressed liquidof, for example, supersaturated gas-dissolved water in which the gas tobe supersaturated is dissolved.

Referring back to FIG. 12, bubbles are generated (S300).

In detail, referring to the example of FIGS. 1 to 3, the orifices 220may be closed until the mixture M is supersaturated and then may beopened when the mixture is supersaturated. Accordingly, the mixture Mmoves from the pressurizing portion 100 to the plasma reaction tank 300through the orifice 220.

Here, since the pressurizing portion 100 has a width much greater thanthe width of the orifice 220, a pressure applied to the mixture M may berapidly decreased. Particularly, since the mixture M has a high pressurein the pressurizing portion 100 due to the pressurizing pump, pressuresthereof in the bubble forming portion 200 and the plasma reaction tank300 may be much lower than that in the pressurizing portion 100.

Accordingly, bubbles B may be formed in the mixture M in the plasmareaction tank 300. The bubbles B may be bubbles of a gas injectedthrough the gas inlet 110. That is, the gas may be present in thebubbles B.

Referring back to FIG. 12, cleaning water including bubble liquid plasmais formed (S400).

In detail, referring to the example of FIGS. 1, 4, and 5, the ignitionelectrode 330 may ignite the bubbles B in the mixture M. The ignitionelectrode 330 may be connected to the power source 350 by the wiring370. The ignition electrode 330 may be covered by the third coating 331.The third coating 331 may shield the ignition electrode 330 so as toblock and prevent the cleaning solution S or the mixture M from cominginto direct contact with the ignition electrode 330.

The plasma reaction tank 300 may initially connect the power source 350to the ignition electrode 330 prior to the second electrode 320. Throughthis, the ignition electrode 330 may ignite plasma so as to formignition plasma in a first region R1.

Sequentially, the plasma reaction tank 300 may close the switch 360 soas to connect the power source 350 to the second electrode 320. Throughthis, the first electrode 310 and the second electrode 320 may applyvoltages to the mixture M and the bubbles B therebetween. Active plasmamay be formed in a second region R2 by using the applied voltages.

The plasma reaction tank 300 may apply a voltage to the mixture M usingthe above-described method. Accordingly, a gas in the bubbles B of themixture M may be converted into plasma. Such plasma is referred to hereas bubble liquid plasma. The plasma reaction tank 300 may convert themixture M into the cleaning solution S including the bubble liquidplasma.

The cleaning solution S may include radicals which are dissolved in thebubble liquid plasma. The radicals may be dissolved in the cleaningsolution S in the bubble liquid plasma while the cleaning solution Scirculates through the plasma reaction tank 300, the first pipe 400, thestorage tank 500, the radical sensor 600, the second pipe 700, thepressurizing portion 100, and the bubble forming portion 200.

Referring back to FIG. 12, the radicals are monitored (S410).

In detail, referring to the examples of FIGS. 1 and 7, the plasmamonitoring device 900 according to some exemplary embodiments of thepresent disclosure measures a type and a concentration of radicals byusing an electrical measuring method. The electrical measuring methodmonitors the type and concentration of radicals by analyzing electricalproperties of liquid plasma including a dielectric. That is, theelectrical measuring method may electrically analyze densities andproperties of the bubbles B and plasma. For this, the plasma monitoringdevice 900 may include a power source and an electrode (not shown).Through this, a voltage or a current may be applied to the cleaningsolution S and electrical characteristics such as resistance may bedetected so as to measure the type and the concentration of theradicals.

In another example, the plasma monitoring device 900 according to someexemplary embodiments of the present disclosure measures a type and aconcentration of radicals by using a microwave analysis method. Themicrowave analysis method may analyze a density of in-liquid plasma byutilizing wave dispersion relation of microwaves.

In another yet example, as described previously in connection with FIG.7, the plasma monitoring device 900 according to some exemplaryembodiments of the present disclosure may measure a type and aconcentration of radicals by using an optical analysis method, in whichcase the plasma monitoring device 900 may be a measuring module usingoptical emission spectroscopy (OES).

Referring back to FIG. 12, the cleaning water is circulated (S500).

In detail, referring to the example of FIG. 1, the circulation pump 710may allow the cleaning solution S to circulate in an order of thepressurizing portion 100, the bubble forming portion 200, the plasmareaction tank 300, the first pipe 400, the storage tank 500, the radicalsensor 600, and the second pipe 700.

A movement direction and velocity of the cleaning solution S may bedefined by the circulation pump 710. Although the circulation pump 710is shown as being located in the second pipe 700 in FIG. 1, thecirculation pump 710 is not limited this particular location.

The circulation pump 710 may be attached at any position in which thecleaning solution S is present, for example, in the first pipe 400 orthe storage tank 500.

Referring back to FIG. 12, a concentration of radicals is sensed (S600).

In detail, referring to the example of FIG. 1, the radical sensor 600may sense the concentration of radicals of the cleaning solution S inthe storage tank 500. The radical sensor 600 may sense the concentrationof radicals of the cleaning solution S by using a variety of methods.

For example, as described previously, the radical sensor 600 may sensethe concentration of radicals of the cleaning solution S by using aspectroscopic method. The spectroscopic method may be a method ofmeasuring a generation speed and a dissipation speed of a radicalreaction product, a consumption factor, or a detected compound usingNDIR or IR spectroscopy. Through this, the radical sensor 600 mayquantitatively analyze radicals of the cleaning solution S.

As another previously described example, the radical sensor 600 of thecleaning solution production system according to some exemplaryembodiments of the present disclosure may measure the concentration ofradicals by using EPR. EPR may measure a type and a concentration ofradicals by using a magnetic moment measuring method using holes ofradicals or spins of electrons. Through this, the radical sensor 600 mayquantitatively and qualitatively analyze radicals of the cleaningsolution S.

Referring back to FIG. 12, here, when the concentration of the radicalsdoes not reach a reference concentration, the cleaning solution S may becontinuously circulated until the concentration of the radicals reachesthe reference concentration.

When the concentration of the radicals reaches the referenceconcentration, the cleaning solution S is discharged (S700). Forexample, the cleaning solution S is discharged to clean a semiconductorsubstrate or wafer as described previously.

In detail, referring to the example of FIG. 1, when it is determinedthat a concentration of particular radicals in the cleaning solution Sreaches the reference concentration, the radical sensor 600 may open thefirst valve 810 and may close the second valve 820.

Through this, the cleaning solution S located in the storage tank 500may move to the nozzle 800. Also, the cleaning solution S whichcirculates from the storage tank 500 to the radical sensor 600 may notfurther circulate.

The nozzle 800 may be connected to the storage tank 500. The nozzle 800may eject the cleaning solution S including radicals onto a wafer W.

Hereinafter, an example of the cleaning water forming operation (400) ofFIG. 12 according to some exemplary embodiments of the presentdisclosure will be described with reference to FIGS. 8, 9, 12, and 13.

Referring to FIG. 13, plasma is generated in a first sub-region by afirst electrode and a first ignition electrode (S401).

In detail, referring to the example of FIGS. 8 and 9, the plasmareaction tank 300 may connect the power source 350 to only the firstignition electrode 330-1 first by closing the first switch 361. Throughthis, the first ignition electrode 330-1 may ignite plasma so as to formignition plasma in a first sub-region R1-1. Here, the second switch 362and the switch 360 may be opened.

Referring back to FIG. 13, plasma is generated in a second sub-region bythe first electrode, the first ignition electrode, and the secondignition electrode (S402).

In detail, referring to FIGS. 8 and 9, the plasma reaction tank 300 mayconnect the power source 350 to the second ignition electrode 330-2first by closing the second switch 362. Through this, the secondignition electrode 330-2 may ignite plasma so as to form ignition plasmain the second sub-region R1-2. Here, the switch 360 may be opened.

As described previously, the second sub-region R1-2 may be larger thanthe first sub-region R1-1 and may be smaller than a second region R2formed between the first electrode 310 and the second electrode 320.When the second switch 362 is closed, the first switch 361 may remainclosed.

Referring back to FIG. 13, plasma is generated in the second region bythe first electrode, the first ignition electrode, the second ignitionelectrode, and the second electrode (S403).

In detail, referring to the example of FIGS. 8 and 9, the plasmareaction tank 300 may close the switch 360 so as to connect the powersource 350 to the second electrode 320. Through this, the firstelectrode 310 and the second electrode 320 may apply voltages to themixture M and the bubbles B therebetween. Active plasma may be formed inthe second region R2 by using the applied voltages. When the switch 360is closed, the first switch 361 and the second switch 362 may remainclosed.

1. A cleaning solution production system for cleaning a semiconductorsubstrate, comprising: a pressure tank; a plasma reaction tankconfigured to form a plasma in gas bubbles suspended in a decompressedliquid obtained from the pressure tank to thereby generate radicalspecies in the decompressed liquid; a storage tank configured to store acleaning solution containing the radical species generated in the plasmareaction tank; and a nozzle configured to supply the cleaning solutionfrom the storage tank to a semiconductor substrate.
 2. The system ofclaim 1, further comprising: a sensor for sensing a concentration of theradical species in the cleaning solution; and a first valve which isresponsive to the concentration sensed by the sensor to selectivelyapply the cleaning solution to the semiconductor substrate via thenozzle.
 3. The system of claim 2, further comprising a second valvewhich is responsive to the concentration sensed by the sensor toselectively transfer the cleaning solution to the pressure tank forrecirculation through the system.
 4. The system of claim 3, furthercomprising a circulation pump operatively connected between the secondvalve and the pressure tank.
 5. The system of claim 1, furthercomprising a bubble formation device interposed between the pressuretank and the plasma reaction tank.
 6. The system of claim 5, wherein thebubble formation device is a plate including a plurality of orifices. 7.The system of claim 1, wherein the plasma reaction tank includes firstand second electrodes located at opposite sides of the plasma reactiontank.
 8. The system of claim 7, wherein the first and second electrodesare shielded to prevent any contact with the decompressed liquid withinthe plasma reaction tank.
 9. The system of claim 7, further comprisingan ignition electrode located below and radially between the first andsecond electrodes.
 10. The system of claim 9, wherein, in a first plasmaformation stage, a power source is initially applied to the ignitionelectrode to form plasma in a first region of the plasma reaction tank,and in a second plasma formation stage subsequent the first plasmaformation stage, the power source is applied to the second electrode toform plasma in a second region of the plasma reaction tank.
 11. Thesystem of claim 9, wherein the ignition electrode is shielded to preventany contact with the decompressed liquid within the plasma reactiontank.
 12. The system of claim 9, wherein the ignition electrode is anelongate electrode having a T-shaped cross-section.
 13. The system ofclaim 7, further comprising first and second ignition electrodes locatedbelow and radially between the first and second electrodes.
 14. Thesystem of claim 13, wherein, in a first plasma formation stage, a powersource is applied to the first ignition electrode to form plasma in afirst sub-region of the plasma reaction tank, in a second plasmaformation stage subsequent the first plasma formation stage, the powersource is applied to the second ignition electrode to form plasma in asecond sub-region of the plasma reaction tank, and in a third plasmaformation stage subsequent to the second plasma formation stage, thepower source is applied to the second electrode to form plasma in asecond region of the plasma reaction tank.
 15. The system of claim 1,further comprising a gas inlet configured to supply a gas into thepressure tank, and a liquid inlet configured to supply a liquid into thepressure tank.
 16. The system of claim 15, wherein the gas includes atleast one of O₂, H₂, N₂, NF₃, CxFy, F₂, Cl₂, Br₂, He, and Ar, where xand y are positive integers.
 17. The system of claim 15, wherein theliquid includes water.
 18. The system of claim 17, wherein the gasincludes O₂, and the radical species includes at least one of OH, O, O₂,O₃, HO₂, H₃O, and H.
 19. The system of claim 17, wherein the radicalspecies includes at least one of NO, NO₂, NO₃, CO₂, CO₃, Cl, F, Br, BrO,Cl, ClO, and HF₂.
 20. The system of claim 1, further comprising a plasmamonitoring device configured to monitor a generation of radical speciesin the decompressed liquid of the plasma reaction tank. 21-40.(canceled)